Preparation of glass container for thermoplastic closure

ABSTRACT

A method for sealing a rim-like opening in a glass container is described. The surface of the opening is treated with tin and/or titanium oxide precursors and with or without one or more of the groups consisting of fluorides, sulfur oxides and sulfur oxide precursors and then overcoated with a chromium III organic metallic complex. A membrane comprising a thermoplastic film is pressed onto the coated opening surface and heated to cause glass-plastic adhesion, forming a closure. The coating steps may be applied to glass containers immediately after forming and annealing as appropriate, or may be applied to glass containers taken from storage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 233,056, filed Feb. 10, 1981, now U.S. Pat. No. 4,324,601,which is in turn a continuation-in-part of Ser. No. 086,398, filed Sept.19, 1979, now U.S. Pat. No. 4,260,438.

BACKGROUND OF THE INVENTION

This invention relates to the preparation of glass containers forthermoplastic membrane sealing. Heat activated membrane seals forplastic containers are common in the packaging and canning art.Generally a membrane, which may be a laminate of aluminum foil and athermoplastic polymer, is pressed on the rim of a plastic container andheated to form polymer-polymer adhesive contact. The problem with thismethod when used with soda-lime-silica glass containers is that thefailure of the seal will generally occur within a few days of sealingdue to poor initial adhesion between the glass and the polymer or poordurability of the adhesion.

Substantially improved adhesion between a membrane seal and a containerfinish is obtained by subjecting the finish to a high temperaturetreatment which modifies the finish surface. This high temperaturetreatment preferably is conducted immediately after the containers areformed and comprises contacting the finish with a decomposiblefluorine-containing compound; a compound which decomposes to form ametal oxide; a compound which decomposes to form a sulfur oxide; sulfuroxides; and combinations of the above. These treating materials may beused in any order or combination, or the metal oxide precursor may beused alone.

A sealing closure for the container is formed by pressing a membranecomprising a thermoplastic film onto the container finish and heating toform a glass/plastic adhesive bond. The membrane desirably may be analuminum foil-thermoplastic film laminate. It may also be a polymersheet, a laminate of polymer, a paper/polymer laminate or a laminate ofone or more layers of polymers, metal foil, and paper.

This described technique provides a reliable and secure closure so longas the container finish remains uncontaminated. However, during cold endtreatment of the containers after annealing, it was found that thetreating material, typically an organic polymer, stearate or silicone,would occasionally be deposited on the container finish to the extentthat erratic sealing results were obtained.

SUMMARY OF THE INVENTION

A glass container is first subjected to a hot end treatment in which thefinish, or sealing surface, is modified by a tin or titanium oxidetreatment so as to enhance its adhesion to a thermoplastic closure. Thecontainer is then annealed and the exterior surface of the container iscoated with a lubricity enhancing material which increases the abrasionand scratch resistance of the glass. Contamination of the containerfinish by the lubricity enhancing material is removed by subjecting onlythe finish to a brief heat treatment at a temperature below which flamepolishing, or surface melting, of the glass occurs. A chromium (III)organic metallic complex is then coated on the finish. Thereafter, aclosure seal is formed by pressing a membrane comprising a thermoplasticfilm over the container finish and heating to form a glass-plasticadhesive bond.

Hence, it is an object of this invention to provide a method forobtaining durable seals between a glass container and a thermoplasticmembrane.

It is a further object of this invention to treat the finish of a glasscontainer so as to obtain a dependable and durable seal with athermoplastic material.

A further object of this invention is to remove contaminating materialsfrom the surface-modified finish of a glass container and to obtainreliable adhesion to a thermoplastic closure.

An additional object of the invention is to provide glass containerswith durable seals having long term integrity to enable the commercialpackaging of liquid product in said containers.

A specific object of this invention is to treat the finish of a glasscontainer with a tin or titanium compound to form a tin or titaniumoxide coating, to remove any contaminating material from said coating,and to coat the finish with a chromium (III) organic metallic complex soas to obtain reliable adhesion to a thermoplastic closure.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagrammatic flow sheet showing the steps to prepare a glasscontainer for use in this invention.

FIG. 2 is a partial view--in section of the upper portion of a glasscontainer showing the mode of attaching a metal foil--thermoplastic filmmembrane to the container sealing surface.

DETAILED DESCRIPTION OF THE INVENTION

The invention comprises the preparation of a glass container for usewith a seal comprising a membrane closure as an alternative to, or incombination with, the conventional screw cap for glass containers. Amembrane comprising a thermoplastic polymer is heat sealed to thesealing surface of the glass container. Heat sealing may be accomplishedby pressing the membrane to the glass at a temperature near or above thesoftening point of the thermoplastic but below its melting point as byuse of a heated platen. The membrane may be covered by a plastic ormetal snap-on or screw-on cap prior to or subsequent to sealing. Themembrane desirably may be metal foil-thermoplastic polymer laminate,which allows induction or conduction heating of the laminate.

Without the use of the treatment described herein, a serious problemwith this type of seal is its vulnerability to humidity. Variouscoatings have been applied to overcome this problem, commonly beingmetallic oxides. While the latter may provide a seal sufficient forcommercial purposes, its use in combination with a fluoride or sulfatetreatment is generally preferred.

Treating glass surfaces with sulfur oxides or decomposable fluorinecompounds and treatment with sulfur and fluorine compounds are wellknown. These are shown, for example, in U.S. Pat. No. 3,249,246.Additionally, treatment of glass substrates with chromium organiccompounds for the purpose of improving bonding of the glass surface withorganic polymers is described in U.S. Pat. No. 3,900,689.

However, the use of these methods for improving the stability of apolymer/glass bond in the presence of water vapor, enabling theemployment of a thermoplastic membrane seal for glass containers has notbeen shown. The further treatment of the sealing surface to supply ametal oxide coating before or after the fluorine or sulfur oxidetreatment results in further improvement in glass/polymer bondstability. Contamination of the so-treated finish of a glass containerby contact therewith by conventional cold end lubricity enhancing agentsinterferes with the integrity of a polymer-glass seal. Removal of anylubricity enhancing agent from the sealing surface or finish after metaloxide coating, if such material is employed, and further treatmentthereof with a chromium organic metallic compound results in aremarkable increase in the stability of bond between the membrane sealand the finish. It is to be noted that conventional sealing closures areunaffected by the presence of lubricity enhancing agents of lubriciousmaterials on the container finish. However, large amounts cause capbackoff problems, that is, the cap loosens on the shelf.

Referring now to FIG. 1 there is shown the sequential steps required forpreparing a glass container for use in this invention. A glass containeror jar 1 is formed in the mold 11 of a forming machine at a hightemperature, normally about 1000 to 2000 degrees F., as is conventional.The containers 1 are carried on conveyor 12 to the hot end treater 13wherein the container finish is subjected to a chemical treatment whichrenders the finish surface durably bondable to a thermoplastic membrane.

Although the containers 1 are conveyed immediately from the forming mold11 to the hot end treater 13, they have cooled considerably at thispoint and display a temperature generally in the range of about 800degrees to about 1200 degrees F. While at this temperature, the sealingsurface or finish of the containers is contacted with a material ormaterials which act upon and modify the surface properties of the glass.These materials include generally (1) certain fluorine containingcompounds, and/or sulfur oxides and/or sulfur oxide precursors with (2)tin or titanium compounds which decompose to form metal oxides and thetreatment temperatures.

The fluorine compounds comprise generally these which decompose uponheating to treatment temperatures, i.e., from 800 degrees to about 1200degrees F., and include specifically the alkyl fluorides as, forexample, 1,1-difluoroethane; ammonium fluorides including NH₄ F and NH₄HF₂ ; metal fluorides such as SnF₄, BF₃, AlF₃, and the like; andmetallo-organic fluorides such as NH₄ SnF₃ and (CH₃)₂ SnF₂. Sulfurcompounds useful in this invention include sulfur dioxide, sulfurtrioxide and sulfur compounds, e.g., ammonium persulfate, whichdecompose to sulfur oxides at treatment temperatures. Metal compoundsemployed are those which thermally decompose to form metal oxides andpreferably comprise tin or titanium chlorides.

Hot end treatment is accomplished by impinging the treating material,either as a liquid or gas stream, upon the finish surface.Alternatively, the treating material may be fed as a gas, along with afuel such as natural gas, to a burner and the burner flame directed toplay on the finish surface. Treatment time required is short, on theorder of a few seconds, but extended treatment times do not detract fromresults obtained.

One preferred hot end treatment comprises contacting the finish surfacewith both a fluorine containing compound and a metal oxide precursorsuch as tin tetrachloride. The order of contact makes no significantdifference in the results obtained with either the fluoride compound orthe metal oxide precursor being applied first. The two treatingmaterials may also be simultaneously applied.

After hot end treatment is complete, the containers are passed throughlehr 14, which may be of the tunnel type, where they are slowlyannealed. Containers exit from the lehr at a relatively cooltemperature, on the order of 100 degrees to 300 degrees F., and are nextpassed to cold end treater 15. In treater 15, the exterior surfaces ofthe containers are given a thin coating of a conventional lubricityenhancing material which typically may be an organic polymer such as forexample polyethylene, a stearate, e.g., polyoxyethylene monostearate, asilicone compound or the like. Purpose of the cold end treatment is toincrease resistance of the containers to abrasion, scratching andbursting by rubbing contact during the high speed handling of thecontainers during subsequent filling, capping, labelling and packagingoperations.

During cold end treatment, some of the treating material deposits on thesurface of the container finish even when efforts are made to avoid theresult. Presence of small amounts of lubricity enhancing agents on thefinish surface does not interface with the seal integrity of ordinaryclosures of the screw type and the like. However, these lubricityenhancing agents do tend to interfere with the bonding or adhesion of athermoplastic membrane to the treated glass surface and do in fact causean unacceptable rate of seal failure.

In this invention, containers which have been subjected to a cold endtreatment which leaves at least a residue of lubricity enhancing agenton the finish surface are further treated to remove that agent from thefinish without affecting the thermoplastic-glass bonding propertiesimparted by the hot end treatment. This is accomplished by brieflyexposing the container finish to an intense, directed heat source 16.The heat source may be a gas burner, a laser or any other narrowlydirected but intense source of heat. Exposure time is ordinarily lessthan five seconds and typically is on the order of one to three seconds.In all cases, surface temperature of the finish must not reach flamepolishing temperatures else the effect of the hot end treatment isdestroyed. It is also important to avoid heating of the container sidewalls as that would destroy the effect of the cold end treatment onthose surfaces. Surface temperature of the finish immediately afterexposure to heat source 16 typically is on the order of 250 degrees to350 degrees F. but it is postulated that higher surface temperatureswere reached during the exposure to the heat source.

In one preferred embodiment, heat source 16 is directed at the containerfinish from above at about a 45 degree angle as is shown in the drawing.The container is then rotated to expose equally all of the finishsurface to the heat source.

After the heat treatment of the finish, while it is still hot, coatingof chromium (III) organic metallic complex is spread over the surface byany suitable means, such as roller 17. Suitable chromium complexes arethose described in U.S. Pat. Nos. 3,787,326 and 3,900,689, availablefrom du Pont under the trade name Volan. One such compound specificallyfound useful is the coordination complex of chromium (III) and fumericacid, described in Example 2 of U.S. Pat. No. 3,878,326. Substitutedfumaric trans acids may be employed as well, as shown in this patent.Such trans acids have the formula ##STR1## R₁ and R₂ are the same ordifferent and maybe H, alkyl, --CH₂ COOH or phenyl; provided that thetotal number of carbon atoms is in the range of 4 to 10.

After treatment of the finish surface is complete and the surface hascooled, as shown in FIG. 2, a laminate of aluminum foil 3 andthermoplastic film 2 is placed on the rim of jar 1 with thethermoplastic film 2 contacting the glass rim, a plastic snap cover 4 isplaced over the jar mouth as shown, to force the laminate in contactwith the rim. A resilient pad 5, is placed over the snap cover and awater-cooled induction heating coil 7, in a chuck or holder 6 ofinsulating material is placed over pad 5. Thereafter high frequencyalternating current is passed through the induction coil to heataluminum foil 3 and cause the thermoplastic film 2 to bond to the glassrim along sealing surface 8.

While the above description is directed to glass containers leaving themold of a forming machine, the process for improving the stability ofthe glass/polymer bond is equally applicable to glass containers moregenerally, e.g., containers taken from storage. Those containers havinga lubricious coating are treated to remove contaminants from the sealingsurface, as by heating. The containers, in a manner similar to thatdescribed above, are coated with a chemical agent comprising tin and/ortitanium oxide precursors, with or without fluorine and/or sulfur oxideand sulfur oxide precursors to form the metal oxide coating. Thereafterthe surface is coated with a chromium (III) organic metallic complex.

The following examples set out specific embodiments which serve to morefully illustrate and explain the invention.

EXAMPLE 1

Ten-ounce capacity round glass jars were sealed without treatment of thesealing surface. The jars were sealed with a Surlyn laminated foil usingan induction heater, at a pressure of 200 psi. Surlyn is a productavailable from du Pont comprising ionomers based on Na or Zn salts ofethylene/methacrylic acid copolymers. The duration of the inductionheating is adjusted in order that the radius of the ring ofthermoplastic softening is approximately half of the radius of theentire closure. The induction field heats from the outer radius first,leaving a ring of melted thermoplastic. Thereafter, the sealed jars weretested for seal durability.

The test used for determining seal durability consisted of sealing jarscontaining small amounts of water and thereafter, allowing the jars toremain at ambient temperature and humidity in an inverted position.

The evaluation of the state of the seals was performed twice weeklyaccording to the following procedure; the sealed jars were placed in avacuum chamber and subjected to a vacuum of 7 inches of mercury for aduration of 15 seconds. The survivors were thereafter returned toambient testing conditions.

Six jars sealed as previously described were subjected to the testconditions and were vacuum evaluated as described above. The results ofthis test are set out in the following table:

                  TABLE I                                                         ______________________________________                                        Vacuum Evaluation,                                                                        Number of Survivors                                                                          Number of Failures                                 Days After Sealing                                                                        of the Evaluation                                                                            of the Evaluation                                  ______________________________________                                        3           0              6                                                  ______________________________________                                    

EXAMPLE 2

Containers were treated with tin tetrachloride vapors during theirmanufacture according to normal production procedures. The containerschosen for testing had a tin oxide layer on the sidewalls of a thicknessbetween 20 and 40 coating thickness units. Such units are standard unitsfor the measurement of the depth of the tin oxide layer and are equal toabout 0.8 angstroms. The containers were sealed and tested as previouslydescribed in Example 1.

The following table gives the results of the above test.

                  TABLE II                                                        ______________________________________                                                       Number of   Number of                                          Vacuum Evaluation,                                                                           Survivors of                                                                              Failures of                                        Days After Sealing                                                                           the Evaluation                                                                            the Evaluation                                     ______________________________________                                        RUN 1                                                                          5             10          0                                                   8             10          0                                                  11             10          0                                                  15             8           2                                                  19             7           1                                                  22             5           2                                                  25             4           1                                                  29             4           0                                                  32             3           1                                                  36             1           2                                                  39             1           0                                                  43             0           1                                                  RUN 2                                                                          4             10          0                                                   7             10          0                                                  10             10          0                                                  14             9           1                                                  18             9           0                                                  21             7           2                                                  24             5           2                                                  28             4           1                                                  31             3           1                                                  35             1           2                                                  38             0           1                                                  RUN 3                                                                          4             10          0                                                   8             6           4                                                  11             6           0                                                  19             4           2                                                  25             3           1                                                  29             3           0                                                  32             2           1                                                  36             1           1                                                  39             0           1                                                  RUN 4                                                                          4             10          0                                                   7             9           1                                                  11             9           0                                                  15             7           2                                                  18             6           1                                                  21             5           1                                                  24             2           3                                                  27             2           0                                                  31             1           1                                                  34             1           0                                                  38             1           0                                                  41             0           1                                                  ______________________________________                                    

EXAMPLE 3

Nine untreated jars identical to those tested in Example 1 were chosenfor the following treatment. Each jar was rotated under an air, naturalgas torch, the burner flame playing on the rim of the jar for 15seconds. Immediately, thereafter, chromium III fumerate (Volan) wasdabbed uniformly onto the sealing surface. Thereafter, the jaw wascooled, sealed, and tested as described in Example 1.

The following table shows the results of this test:

                  TABLE III                                                       ______________________________________                                                       Number of   Number of                                          Vacuum Evaluation,                                                                           Survivors of                                                                              Failures of                                        Days After Sealing                                                                           the Evaluation                                                                            the Evaluation                                     ______________________________________                                        4              6           3                                                  8              4           2                                                  11             0           4                                                  ______________________________________                                    

EXAMPLE 4

Ten tin tetrachloride treated samples prepared as described in Example 2were treated with Volan as described in Example 3. Thereafter, the jarswere sealed and tested as described in Example 1.

The following table gives the results of the above tests:

                  TABLE IV                                                        ______________________________________                                                       Number of   Number of                                          Vacuum Evaluation,                                                                           Survivors of                                                                              Failures of                                        Days After Sealing                                                                           the Evaluation                                                                            the Evaluation                                     ______________________________________                                         3             10          0                                                   6             10          0                                                  10             10          0                                                  13             10          0                                                  16             10          0                                                  20             9           1                                                  23             9           0                                                  26             9           0                                                  29             9           0                                                  33             8           1                                                  37             8           0                                                  40             8           0                                                  43             8           0                                                  47             8           0                                                  52             7           1                                                  54             6           1                                                  57             6           0                                                  61             6           0                                                  65             5           1                                                  68             5           0                                                  73             3           2                                                                             0                                                  80             2           1                                                  83             2           0                                                  91             2           0                                                  97             2           0                                                  101            2           0                                                  104            2           0                                                  108            2           0                                                  111            2           0                                                  118            2           0                                                  126            2           0                                                  132            2           0                                                  136            2           0                                                  141            2           0                                                  143            1           1                                                  146            1           0                                                  150            1           0                                                  153            0           1                                                  ______________________________________                                    

The improved jar top closure of the present invention has significantadvantages over the conventional closures now employed, e.g., plastic ormetal screw-on caps. Good durable seals are produced for many liquidproducts, such as salad dressing, honey, syrups, ketchup and spaghettisauce. Since the membrane seal must be broken to remove the contents,the container is tamper evident. The snap-cap and foil plastic sealsystem is economical and results in considerable savings overconventional sealing systems. Since the sealing membrane is flexible andis in adhesive contact with the container at its rim portion, thecontainer opening may have a large number of shapes. For example, it maybe oval, square, have a pour spout, etc.

Elimination of the necessity for screw threads enables the use ofcontainers having more aesthetic designs, which can be employed forother purposes such as vases, etc. after they are emptied. The membraneclosure eliminates any torque problems due to the sticking of a screwcap, and avoids rusting and corrosion difficulties.

We claim:
 1. A method for preparing the surface of a rim-like opening ina glass container for use with a thermoplastic membrane, said rim-likeopening having a sealing surface, comprising:removing any contaminantmaterial, if present, from the sealing surface; treating said surfacewith a chemical agent comprising at least one metal oxide precursorselected from the group consisting of tin oxide and titanium oxideprecursors and mixtures thereof and forming, respectively, a tin ortitanium oxide or a mixture thereof coating on said surface,.Iadd.overcoating said tin or titanium oxide or a mixture thereofcoating on said surface by .Iaddend.applying a chromium (III) organicmetallic complex to said surface.
 2. The method of claim 1 wherein thechromium (III) organic metallic complex is a trans acid having theformula ##STR2## wherein R₁ and R₂ may be the same or different, R₁ andR₂ may be H, alkyl, --CH₂ COOH or phenyl, and the total number of carbonatoms is an integer in the range of 4 to
 10. 3. The method of claim 2wherein the chemical agent comprises in addition zero to one or more ofa composition selected from the group consisting of fluorine compounds,sulfur oxides and sulfur oxide precursors and mixtures thereof, the saidtreatment with the chemical agent being conducted at an elevatedtemperature below the flame polishing temperature.
 4. The method ofclaim 3 wherein the metal oxide precursor compound is selected from amember of the group consisting of tin chlorides and titanium chlorides.5. The method of claim 4 wherein the fluorine compound is a member ofthe group consisting of NH₄ SnF₃, (CH₃)₂ SnF₂, alkyl fluorides, SnF₄,BF₃, AlF₃, NH₄ F and NH₄ HF₂.
 6. The method of claim 5 wherein the transacid is fumaric acid.
 7. The method of claim 6 wherein the chemicalagent employed in treating the surface is essentially a tin chloride. 8.The method of claim 6 wherein the chemical agent employed in treatingthe surface is essentially a titanium chloride.
 9. The method of claim 6wherein the chemical agent employed in treating the surface isessentially a mixture of tin and titanium chlorides.
 10. A method forpreparing the finish of a glass container including side walls for usewith a thermoplastic membrane closure comprising:subjecting thecontainer finish while hot after forming and before annealing totreatment with a chemical agent comprising contacting said containerfinish with a metal oxide precursor selected from the group consistingof tin oxide and titanium oxide precursors and mixtures thereof whichdecompose to form materials comprising tin oxide, titanium oxide andmixtures thereof, respectively, at the container temperature, whichrenders the finish surface adherable to a thermoplastic membrane;annealing said container; subjecting the annealed container to a coldend treatment wherein the exterior container including the side walls iscoated with a lubricity enhancing agent, and removing said lubricityenhancing agent from the finish surface by briefly exposing said surfaceto an intense heat source and heating it to below flame polishingtemperature while avoiding the destruction by heat of the effect of thecold end treatment on the side walls, and thereafter coating the finishwith a chromium (III) organic metallic complex.
 11. The method of claim10 wherein the chromium (III) organic metallic complex is a chromium IIIcomplex of a trans acid having the formula ##STR3## wherein R₁ and R₂may be the same or different, R₁ and R₂ may be H, alky, --CH₂ COOH orphenyl, and the total number of carbon atoms is an integer in the rangeof 4 to
 10. 12. The method of claim 11 wherein the finish surface isexposed to the intense heat source by rotating beneath a gas burner fora time of less than about five seconds.
 13. The method of claim 11wherein the chemical agent comprises in addition zero to one or morecompositions selected from the group consisting of fluoride compoundsdecomposable at the hot container temperature, sulfur oxides and sulfuroxide percursors decomposable at the hot container temperature.
 14. Themethod of claim 13 wherein said metal oxide precursor is selected fromthe group consisting of tin chlorides and titanium chlorides.
 15. Themethod of claim 14 wherein said fluoride compound consists of at leastone member of the group consisting of NH₄ SnF₃, (CH₃)₂ SnF₂, alkylfluorides, SnF₄, BF₃, ALF₃, NH₄ F and NH₄ HF₂.
 16. The method of claim15 wherein the trans acid is fumaric acid.
 17. The method of claim 16wherein the chemical treatment is essentially with a tin chloride. 18.The method of claim 16 wherein the chemical treatment is essentiallywith a titanium chloride.
 19. The method of claim 16 wherein thechemical treatment is essentially with a mixture of tin and titaniumchlorides.
 20. A method for sealing an opening in a glass containerhaving side walls comprising:providing a rim-like sealing surface aroundsaid opening; treating said sealing surface at a high temperature with achemical agent comprising a metal oxide precursor selected from thegroup consisting of tin oxide and titanium oxide precursors and mixturesthereof which decomposes to form tin oxide, titanium oxide and mixturesthereof, respectively, at the container temperature, which renders saidsurface adherable to a thermoplastic membrane; coating the exteriorsurface of said container including said side walls with a lubricityenhancing agent; removing said lubricity enhancing agent from only saidsealing surface by briefly exposing said surface to an intense heatsource and heating it to below flame polishing temperature whileavoiding destruction by heat of the effect of the lubricity enhancingtreatment on the side walls, thereafter coating the finish surface witha chromium (III) organic metallic complex, and pressing a membranecomprising a thermoplastic material against said sealing surface at atemperature above the softening point but below the melting point ofsaid thermoplastic.
 21. The method of claim 20 wherein the chromium(III) organic metallic complex is a chromium III complex of a trans acidhaving the formula ##STR4## wherein R₁ and R₂ may be the same ordifferent, R₁ and R₂ may be H, alky, --CH₂ COOH or phenyl, and the totalnumber of carbon atoms is an integer in the range of 4 to
 10. 22. Themethod of claim 21 wherein the chemical agent comprises in addition zeroto one or more compositions selected from the group consisting offluoride compounds decomposable at the hot container temperature sulfuroxides and sulfur oxide precursors decomposable at the hot containertemperature.
 23. The method of claim 22, wherein said metal oxideprecursor is selected from the group consisting of tin chlorides andtitanium chlorides.
 24. The method of claim 23 wherein said fluoridecompound consists of at least one member of the group consisting of NH₄SnF₃, (CH₃)₂ SnF₂, alkyl fluorides, SnF₄ BF₃, ALF₃, NH₄ HF₂.
 25. Themethod of claim 24 wherein the trans acid is fumaric acid.
 26. Themethod of claim 25 wherein the high temperature treatment with achemical agent is essentially with a tin chloride.
 27. The method ofclaim 25 wherein the high temperature treatment with a chemical agent isessentially with a titanium chloride.
 28. The method of claim 25 whereinthe high temperature treatment with a chemical agent is essentially witha mixture of tin and titanium chlorides.
 29. The method of claim 20wherein said container is annealed after treatment with said chemicalagent but before coating the exterior surface thereof with a lubricityenhancing agent.
 30. The method of claim 20 wherein the lubricityenhancing agent is removed from said sealing surface by rotating saidsurface beneath a gas burner for a time of about five seconds.
 31. Themethod of claim 20 wherein said membrane comprises a thermoplastic filmadhesively joined on one face to a metal foil.
 32. The method of claim20 wherein said glass is a soda-lime-silica glass.